If you upload several receipts from the same "Retailer", with the same "Purchase Date" and within 10-minute intervals, the system will merge all the receipts in this time period, sum the total and assign points based on the summed total. This is determined by the purchase date printed on the receipts, not the date when you uploaded the receipt.
You will notice that you do get points for one of the receipts.
This is to prevent receipt-splitting behaviours, i.e. intentionally splitting up one single purchase into multiple transactions to get multiple receipts.